1. There is possibly several ways to game the upvote system. HN community is not anonymous, and there are people who have more friends here than others. A lot of very good founders would probably not have enough friends here. That might create bias once an Apply HN post reaches first page vs. another.
2. Participating startups risk facing public bashing while hoping to get priceless feedback. This happens often here, even unintentionally sometimes. This also poses a risk that a lot of startups would not be 100% honest in one way or another to minimize bashing. This is commonplace on Reddit. But this is not Reddit and any founder cannot forever escape people here. This is an ecosystem forum which is extremely civil in Show HN (with a few exceptions) but might not be so when competing for a resource -- the 2 YCF spots. Maybe Reddit is the way it is because everyone is competing for points.
3. Publicly applying for funding might step on private financing laws of several states and nations? It might also be against some by-laws. Would this constitute a public offer?
Maybe this could be helped better by doing one or more of these:
1. Apply HN posts should not make it to homepage and should be a separate section.
2. The heuristic should not be known publicly of what YC partners are looking for.
3. Companies should still be required to fill a YC app before posting. Then it's a public contest rather than a public offer to sell shares.
This would be interesting for sure!